1. Technical Field
The present invention relates to the field of optical coherence tomography (OCT) systems, and more particularly, to an OCT system implementing multiple viewing and processing configurations.
2. Discussion of Related Art
FIG. 1A illustrates an Optical Coherence Tomography (OCT) system 50 according to prior art. OCT system 50 comprises a light source 90, e.g. a broadband (white) light source, which is used to generate a light beam. OCT system 50 further comprises a low-coherence interferometer 72 including e.g. a beam splitter 70 (as part of a Michelson interferometer), to split the light beam into a sample beam directed at a sample 80 and reflected therefrom, and a reference beam which may be directed at a mirror 85 and reflected therefrom. Interferometer 72 is arranged to receive the reflections of the sample beam and the reference beam, and create an interference pattern which is measured by a detector 95, such as a photodiode. Because of the source's wide spectral bandwidth, an interference pattern will emerge only if the pathlength between light reflected from the reference and sample arms are within the temporal coherence length of the source. A depth-scan (A-scan) can be formed under various configurations. A time domain OCT image physically scans the reference arm in the axial direction, thereby changing the delay and enabling probing different depths in the sample. A spectral domain OCT image keeps the reference arm position constant but replaces the detector with a spectrometer consisting of a dispersive element such as a prism for example, coupled to a detector line array such as a CCD camera. The A-scan is found from the inverse Fourier transform of the spectral interference pattern. Alternatively, the spectral interference pattern can also be attained while keeping the reference arm position fixed and while using a point detector by scanning (or “sweeping” or “tuning”) the light source through narrow monochromatic bands. This OCT configuration requires synchronizing detector acquisition times with the instantaneous light source wavelength. In this configuration, known as swept source OCT, the A-scan is also determined from the inverse Fourier transform of the spectral interferogram. Creating a two-dimensional (2D) or three-dimensional (3D) OCT image requires scanning the beam on the sample. The scanning OCT configuration scans the beam between successive A-scans, while the full field OCT acquires from multiple lateral positions in parallel (i.e., an imaging configuration) using a one dimensional (1D) or 2D detector array.
The following documents illustrate aspects of the prior art. Zuluaga and Richards-Kortum 1999 (“Spatially resolved spectral interferometry for determination of subsurface structure”, Optical letters 24:8 pages 519-521) disclose a two-dimensional non-scanning OCT system. U.S. patent application no. 2008/0158550 discloses a non-scanning OCT implementation in two dimensions, and Abdulhalim 2011 (“Non-display bio-optic applications of liquid crystals”, Liquid crystals today 20:2 pages 44-66) discloses a multimodal OCT system implementing a liquid crystal devices to control beam characteristics.